Many systems have been developed for controlling model vehicles, such as cars, boats and the like, on a tether or by remote control means. For true remote control at extended range, radio control is the most practical, but is too expensive for wide spread use and is subject to interference in crowded frequency bands.
Rigid control connections are too restrictive and flexible connections such as strings or cables must be kept under tension for proper control. Cables running inside flexible tubes have been used, but friction is a problem and the controls tend to bind. Unsupported flexible tubes also drag on the ground, causing obstruction and retarding motion. For multiple control functions, the arrangement is completely impractical.